Faced with a surge in COVID-19 cases, some Canadian hospitals are considering plans to sterilize and reuse N95 masks to help stretch out limited supplies.
The specialized masks are usually thrown away after being used only once.
“In an ideal world, we wouldn’t reuse one of these masks,” says Dr. Jerome Leis, medical director of infection prevention and control at Sunnybrook Health Sciences Centre in Toronto.
“But in the context of a crisis, we need to explore this option.”
Personal protective equipment (PPE) – including gloves, gowns, face shields and masks – are considered essential tools for guarding health-care workers from being infected as they look after sick patients.
In most situations, a regular surgical mask is considered sufficient protection against the novel coronavirus – officially called SARS-CoV-2 – which is spread through droplets from coughing, sneezing and possibly talking. The droplets travel only a short distance – about 2 metres – and quickly settle on nearby surfaces.
However, an N95 mask is recommended for “aerosol-generating” medical procedures, such as intubation, in which a tube is inserted into the patient’s airway to assist breathing.
The virus infects and multiplies in the respiratory tract and the lungs. So, a procedure that vigorously disturbs these areas of the body, can “aerosolize” the virus. This means the virus can be temporarily suspended in the air in droplets of various sizes, requiring the need for an N95 mask. This special mask is designed to provide a close facial fit and very efficient filtration of particles in the air.
“We have known that the N95 supply would be a critical issue when we saw that COVID-19 was becoming a pandemic,” says Dr. Leis.
“Some institutions are very vulnerable to running out.”
As a result, hospitals have been considering various ways to conserve this precious resource – including the possibility of cleaning and reusing the disposable masks.
Yet, infectious disease experts haven’t been certain that N95 would provide the same level protection after it has gone through a sterilization process.
But a new study by Canadian researchers, working in collaboration with the National Microbiology Laboratory in Winnipeg, provides encouraging evidence that the masks do maintain their integrity.
The researchers decontaminated four different types of N95 masks using a variety of sterilization methods. They found that the masks were still effective afterwards, although one method – called autoclaving – appears to be superior because it allowed an N95 to be sterilized up to five times and still protect against the pathogen.
“If you have 500 masks left, and you can reprocess them five times, you have the equivalent of 2,500 masks and you can stretch out your supply,” says Dr. Leis. “This is very, very promising.”
The researchers shared their preliminary results by posting them online. Now many hospitals are doing their own feasibility tests, trying to confirm that a mask can be sterilized without losing its structural integrity and effectiveness.
“Each hospital has a different set of the various N95 models that their staff are fit-tested to,” says Dr. Kevin Katz, medical director of infection prevention and control at North York General Hospital in Toronto. “We just want to make sure that whatever we choose to do works for the common masks we tend to use.”
Autoclaving sterilizes through a combination of heat, pressure and steam.
The masks are placed in a sealed chamber which is brought up to a temperature of 121 degrees centigrade. A vacuum pump then removes all the air, and steam is injected into the chamber.
“The steam penetrates every part of the product,” explains Abdool Karim, medical devices reprocessing manager at Sunnybrook. He notes that each mask is in its own porous pouch. After about 30 minutes, the steam is sucked out of the chamber and the cooling down and drying phases get underway.
“The total cycle time is about an hour and 30 minutes,” he says. “We can do about 400 masks in one load and we have three separate steam sterilizers (autoclave machines).”
The key advantage of autoclaving is that most hospitals already have the equipment which is routinely used to clean and sterilize reusable medical devices.
Even so, sterilizing masks raises “logistical questions,” says Dr. Katz. For instance, should one mask be reused by the same health-care worker or should it go to someone else?
What’s more, staff acceptance is critical. “We have to make sure they feel comfortable with it,” he adds.
Dr. Leis notes that the studies involving the National Microbiology Laboratory demonstrated that the SARS-CoV-2 virus had been eradicated by the sterilization process.
In one set of tests, some masks were actually contaminated with the virus and then cleaned. The researchers confirmed the reprocessed masks were free of the pathogen.
He says the researchers were also “very rigorous” in their evaluation of the integrity of the masks which had been sterilized.
Sunnybrook has already started collecting used N95 masks. They are placed in clean self-sealing pouches which are transparent on one side and porous on the other. Staff members are writing their names on the outside of the pouches and on the masks they used.
“The health-care workers who are being asked to reprocess their masks are the same health-care workers who would be without a mask in the future if we were to run out,” says Dr. Leis.
“They are very keen to cooperate if it will ensure they have access to a mask when they need it.”
Dr. Leis adds that reprocessed masks would be used only if the need arises and the existing stock is depleted.
Meanwhile, there is increasing pressure on the supply chain for obtaining new masks. Last week, U.S. President Donald Trump threatened to block the export of vital medical supplies – including N95 masks – so they can be used domestically.
At the same time, a growing number of Canadian health-care organizations say they want their members to have access to N95 masks even though they don’t perform “aerosol-generating” medical procedures.
“I expect we are soon going to see a lot more recommendations, provincially and nationally, to reprocess N95 masks,” says Dr. Leis.
“I think the time to act is now – and not when we have critical shortages. We want our supply to last through this first wave of the pandemic ”